1. Field of the Invention
The present invention relates to an apparatus for obtaining information on an object in a depth direction using optical coherence tomography (OCT) based on spectral interference (using spectral interference), and specifically, relates to an ophthalmic apparatus for obtaining information on an eye in a depth direction.
2. Description of Related Art
There is an apparatus for obtaining information on an object in a depth direction, including a tomographic image, a surface image, a shape and a size of the object, using optical coherence tomography based on spectral interference. This kind of apparatus, for example, obtains the information on the object in the depth direction by irradiating measurement light (object light) being low coherent light onto the object, synthesizing the measurement light reflected from the object and reference light being low coherent light to interfere by an interference optical system, dispersing interference light for every frequency (wavelength) by a spectral optical system, photo-receiving the dispersed interference light with a photodetector and analyzing a photo-receiving signal thereof (see U.S. Pat. No. 6,377,349 corresponding to Japanese Patent Application Unexamined Publication No. HEI11-325849).
By the way, in the above-mentioned apparatus, as for the photodetector which photo-receives the interference light dispersed into frequency components, a predetermined correlation is established between its pixels and the frequency components (for example, the frequency components to be photo-received are allocated to every pixel of the photodetector). However, if there occurs misalignment between an optical member such as a diffraction grating of the spectral optical system and the photodetector, spectral information (light intensity distribution information) detected by the photodetector is changed; therefore, there is a possibility that the information on the object in the depth direction cannot be accurately obtained.